// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
#include <numeric>
#include <stack>
#include <chrono>
using namespace std;
#define int long long
#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define fi first
#define Se second
void fast_io() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
cout << fixed << setprecision(9);
}
template <typename T>
istream& operator>>(istream& in, vector<T>& v) {
for (auto &x : v) in >> x;
return in;
}
template <typename T1, typename T2>
istream& operator>>(istream& in, pair<T1, T2>& p) {
in >> p.first >> p.second;
return in;
}
template <typename T>
void print_single(const T& x) { cout << x; }
template <typename T1, typename T2>
void print_single(const pair<T1, T2>& p) { cout << p.first << ' ' << p.second; }
template <typename T>
void print_vector(const vector<T>& v) {
if (v.empty()) { cout << endl; return; }
if constexpr (is_arithmetic_v<T>) {
for (int i = 0; i < sz(v); i++) {
if (i) cout << ' ';
cout << v[i];
}
cout << endl;
} else {
for (auto &x : v) {
print_single(x);
cout << endl;
}
cout << endl;
}
}
template <typename T>
ostream& operator<<(ostream& out, const vector<T>& v) {
print_vector(v);
return out;
}
template <typename K, typename V>
ostream& operator<<(ostream& out, const map<K, V>& mp) {
for (auto &p : mp) cout << p.first << ' ' << p.second << endl;
cout << endl;
return out;
}
void solve() {
int n, k; cin >> n >> k;
vector<int> a(n); cin >> a;
int match = n, use = n;
vector<int> dif(n - 1);
for (int i = 1; i < n; i++){
dif[i - 1] = (a[i] - a[i - 1] - 1);
}
sort(rall(dif));
while (match > k){
use += dif.back();
match--;
dif.pop_back();
}
cout << use << endl;
return;
}
signed main() {
fast_io();
srand(chrono::steady_clock::now().time_since_epoch().count());
int tc = 1;
// cin >> tc;
while (tc--) solve();
return 0;
}
